Design of a forced-air-twin-chamber for investigating the effects of controlled levels of non-uniformity in heat treatment of tomatoes on product quality

A twin-chambered forced-air apparatus was built to simultaneously apply different environments to each hemisphere of tomato (Lycopersicon esculentum Merr.) fruit. This setup enabled one hemisphere of each fruit to be exposed to an air temperature–velocity combination of 39 °C/0.24 m s−1; while the other hemisphere was simultaneously exposed to a combination of 36 °C/0.24 m s−1, 37 °C/0.24 m s−1, or 36 °C/0.12 m s−1. Tomato fruits were divided into four lots: one left untreated; two lots were uniformly heat treated by maintaining the same environment in each chamber; and the remaining were subjected to twin chamber heat treatment. The fruits were then transferred to storage conditions at 14 °C, and allowed to ripen at 20 °C or subjected to chilling injury at 2 °C. The temperature difference between the two chambers significantly influenced the uniformity of color, whereas the firmness, titratable acidity and sugar to acid ratio were only marginally affected. Decreasing the temperature difference between the two chambers or increasing air velocity in heated chamber significantly improved the uniformity of quality.